HTC held an AMAA (Ask Me Almost Anything) on Reddit earlier today/night (depending where you are).
And following was said (about updates to One X/X+):
To address an issue that’s top of mind for many folks here, we recently announced that we wouldn’t be updating the HTC One X and One X+ beyond Android 4.2. Without the support of our chip manufacturer Nvidia, it made a global update of One X and X+ devices impossible. However, in US the One X uses the Qualcomm chip and an upgrade would be possible, but we didn’t think it would be a good experience for our customer base to update the X, but not the X+. This update caused a huge stir amongst owners and we’ve heard you loud and clear, so we’re now actively exploring how we can make the jump to 4.4.
This means that EMEA/APAC One X/X+ WILL stay on 4.2.2/Sense 5 since they both have the Nvidia Tegra 3 SoC. American One X+ will stay on the same version as the EMEA/APAC variant as it shares the same SoC, but since the American One X got the Qualcomm SoC HTC said”we’re now actively exploring how we can make the jump to 4.4.”. So, it sadly means that the EMEA/APAC One X will stay where it is.